Solar tower system with carousel heliostats

Abstract

A solar tower system including an array of individually controlled carousel-type heliostats, where each heliostat includes a rotatable D-shaped carousel, a mirror array including horizontal, elongated flat mirrors supported in a tiltable (e.g., louvered) arrangement on the carousel, and a mirror positioning system that is disposed next to the carousel and controls the tilt position of each mirror and a rotational position of the carousel to reflect light onto a solar receiver. The heliostats are arranged in a closely-spaced (e.g., square or hexagonal) pattern that both maximizes the effective ground coverage ratio of solar power harvesting system and facilitates the formation of service pathways that allow access to any of the heliostats in the array (e.g., by aligning the straight peripheral wall portions of adjacent carousels in parallel with each other).

The invention claimed is: 
     
       1. A solar tower system comprising:
 a solar receiver fixedly disposed over a support surface; 
 an array including a plurality of heliostats disposed on the support surface adjacent to the solar receiver, each heliostat including:
 a rotatable carousel having a substantially D-shaped base including a peripheral edge structure surrounding a central region, the base being disposed on the support surface such that the peripheral edge structure is rotatatable around a central axis located in the central region, 
 a mirror array including a plurality of elongated flat mirrors arranged in a low-profile, substantially horizontal plane and disposed in the central region, each elongated flat mirror being movably connected to and simply supported between corresponding portions of the peripheral edge structure such that said each elongated flat mirror is maintained in a corresponding tilt angle; and 
 a mirror positioning system fixedly disposed on the support surface adjacent to the carousel, the mirror positioning system including:
 a solar elevation tracking controller including means for adjusting the tilt angle of each of the plurality of elongated flat mirrors in accordance with a determined sun elevation angle such that sunlight directed onto the mirror array from said determined sun elevation angle is reflected by all of the plurality of elongated flat mirrors onto the solar receiver, and 
 a solar azimuth tracking controller including means operably connected to the peripheral wall for adjusting the rotational position of the carousel around the central axis in accordance with a determined sun azimuth angle such that sunlight directed onto the mirror array from said determined sun azimuth angle is reflected by all of the plurality of elongated flat mirrors onto the solar receiver. 
 
 
 
     
     
       2. A solar tower system of  claim 1 ,
 wherein the substantially D-shaped peripheral edge structure of each said heliostat comprises a curved wall portion and a straight wall portion connected across edges of the curved wall portion, and 
 wherein the solar azimuth tracking controller of each said heliostat includes a drive mechanism operably coupled to said curved wall portion. 
 
     
     
       3. A solar tower system of  claim 2 ,
 wherein each said heliostat further comprises one or more tilt-angle control mechanisms disposed on the peripheral edge structure and connected to said mirror array such that each elongated flat mirror is connected to the tilt-angle control mechanism, and 
 wherein the solar elevation tracking controller of said each heliostat further includes means for manipulating the tilt-angle control mechanism such that the tilt angle of each of the plurality of elongated flat mirrors is adjusted by the tilt-angle control mechanism. 
 
     
     
       4. A solar tower system of  claim 3 ,
 wherein the tilt-mechanism of said each heliostat comprises a moveable member that is moveably connected to the peripheral edge structure and defines a plurality of slots, and 
 wherein each elongated flat mirror of each mirror array includes a first rod that is rotatably connected to the peripheral edge structure of said each heliostat, and a second rod that is slidably engaged in a corresponding slot of said plurality of slots such that movement of the movable member in a first direction relative to the peripheral edge structure causes the corresponding tilt angle of said each elongated flat mirror to decrease, and such that movement of the movable member in a second direction relative to the peripheral edge structure causes the corresponding tilt angle of said each elongated flat mirror to increase. 
 
     
     
       5. A solar tower system of  claim 4 , wherein the the solar elevation tracking controller of each said heliostat includes a first motor and associated linkage mechanism for causing said movable member to move away from the peripheral edge structure in order to decrease the corresponding tilt angle of said each elongated flat mirror, and for causing said movable member to move toward the peripheral edge structure in order to increase the corresponding tilt angle of said each elongated flat mirror. 
     
     
       6. A solar tower system of  claim 4 , wherein the solar elevation tracking controller of each said heliostat comprises:
 a device for determining a sun elevation angle, 
 a processor for generating control signals in response to the determined sun elevation angle, and 
 a motor for supplying a positioning force to said movable member until the corresponding tilt angle of said each elongated flat mirror causes said each elongated flat mirror to reflect sunlight onto said solar receiver of a solar power harvesting system. 
 
     
     
       7. A solar tower system  claim 1 , wherein said carousel of each said heliostat further comprises a passive movable support mechanism disposed between the base and the support surface. 
     
     
       8. A solar tower system  claim 7 , wherein each said heliostat further comprises a curved guide disposed on the support surface, wherein the movable support mechanism comprises a plurality of support wheels, each support wheel of the plurality of support wheels being engaged with the curved guide such that said each wheel is constrained to move along a path defined by a curved guide. 
     
     
       9. A solar tower system of  claim 7 , wherein the solar azimuth tracking controller of each said heliostat comprises:
 a device for determining a sun azimuth angle, 
 a processor for generating a control signal in response to the determined sun azimuth angle, and 
 a motor for supplying a positioning force to said peripheral edge structure such that the carousel rotates by way of said passive movable support mechanism until the corresponding rotational position of the carousel causes said plurality of elongated flat mirror to reflect sunlight onto said solar receiver of a solar power harvesting system. 
 
     
     
       10. A solar tower system of  claim 3 ,
 wherein the base of each said heliostat comprises a first continuously curved wall portion and a straight wall portion connected across edges of the first continuously curved wall portion, 
 wherein the solar azimuth tracking controller of each said heliostat comprises means for supplying a positioning force to said first continuously curved wall portion such that the carousel is rotated around the central axis into a first said rotational position in accordance with a determined sun azimuth angle, 
 wherein the tilt-mechanism of each said heliostat comprises a second continuously curved wall portion and a second straight wall portion connected across edges of the second continuously curved wall portion, wherein the second continuously curved wall portion is concentrically disposed and supported by the first continuously curved wall portion, and 
 wherein the elevation tracking controller of each said heliostat includes means for causing said second continuously curved wall portion to move vertically relative to the first curved wall portion such that each elongated flat mirror is tilted into a first corresponding tilt angle in accordance with a determined sun elevation angle. 
 
     
     
       11. A solar tower system of  claim 10 ,
 wherein the second continuously curved wall portion of the tilt-mechanism of each said heliostat defines a plurality of slots, and 
 wherein each elongated flat mirror of the mirror array of each said heliostat includes a first rod that is rotatably connected at each end to the first continuously curved wall portion, and a second rod that is slidably engaged at each end into corresponding slots of said plurality of slots such that concentric movement of the second continuously curved wall portion in a first direction relative to the first curved wall portion causes the corresponding tilt angle of said each elongated flat mirror to decrease, and such that concentric movement of the second continuously curved second wall in a second direction relative to the first continuously curved wall portion causes the corresponding tilt angle of said each elongated flat mirror to increase. 
 
     
     
       12. A solar tower system of  claim 10 ,
 wherein each said heliostat further comprises: 
 a plurality of rollers fixedly secured to an outside surface the continuously curved wall portion, and 
 a plurality of wedge structures disposed on an outside surface of the second continuously curved wall portion, and 
 wherein the second continuously curved wall portion of each said heliostat is concentrically mounted on the first continuously curved wall portion of each said heliostat such that each wedge structure of the plurality of wedge structures is supported on an associated roller of the plurality of rollers, and such that rotation of the second continuously curved wall portion relative to the first continuously curved wall portion around the central axis causes said each roller to roll along said associated wedge, whereby said second continuously curved wall portion moves in the direction of the central axis relative to the first continuously curved wall portion. 
 
     
     
       13. A solar tower system of  claim 10 ,
 wherein the solar azimuth tracking controller of each said heliostat comprises a first motor operably coupled to the first continuously curved wall portion such that force generated by the first motor causes the first continuously curved wall portion to rotate around the central axis, and 
 wherein the solar elevation tracking controller comprises a second motor operably coupled to the second continuously curved wall portion such that force generated by the second motor causes the second continuously curved wall portion to rotate around the central axis, 
 whereby controlling said first and second motors such that a rate of rotation of the first continuously curved wall portion is different from a rate of rotation of said second continuously curved wall portion causes said each roller to roll along said associated wedge. 
 
     
     
       14. A solar tower system of  claim 2 , wherein the plurality of heliostats are arranged in a closely-spaced pattern, and wherein, when the carousels of said plurality of heliostats are rotated such that the straight wall portions of all of said heliostats are parallel, a service pathway is formed between the carousels that allows access to any said heliostat of said array. 
     
     
       15. A solar tower system of  claim 14 , wherein the closely-spaced pattern comprises a square pattern in which the plurality of heliostats are aligned in a plurality of parallel rows and a plurality of parallel columns on said support surface, and wherein the mirror positioning system of all of said plurality of heliostats in an adjacent pair of said rows are disposed in areas of said support surface located between said plurality of heliostats of said adjacent pair of said rows. 
     
     
       16. A solar tower system of  claim 15 , wherein the mirror positioning system of each of said plurality of heliostats further comprises means for rotating said carousel such that the straight wall portion of each said heliostat is aligned in parallel with said parallel rows and faces away from the mirror positioning system of said each heliostat. 
     
     
       17. A solar tower system of  claim 14 , wherein the closely-spaced pattern comprises a hexagonal pattern in which the plurality of heliostats are aligned in a plurality of offset parallel columns on said support surface, and wherein the mirror positioning system of all of said plurality of heliostats in an adjacent pair of said offset parallel columns are disposed in areas of said support surface located between said plurality of heliostats of said adjacent pair of said offset parallel columns. 
     
     
       18. A solar tower system of  claim 17 , wherein the mirror positioning system of each of said plurality of heliostats of said group further comprises means for rotating said carousel such that the straight wall portion of each said heliostat is aligned in parallel with said offset parallel columns and faces away from the mirror positioning system of said each heliostat. 
     
     
       19. A co-generation power plant utilizing both a solar tower system and a conventional natural gas heat generator to generate steam in a steam production facility that is operably coupled to a steam turbine such that steam generated in the steam production facility drives the steam turbine, wherein the solar tower system comprises:
 a heat-exchange-type solar receiver having a conduit containing a heat transfer fluid, and means for transferring the heat transfer fluid from the solar receiver to a heat exchanger disposed inside the steam production facility; and 
 an array including a plurality of heliostats disposed on a support surface adjacent to the solar receiver, each heliostat including:
 a rotatable carousel having a substantially D-shaped base including a peripheral edge structure surrounding a central region, the base being disposed on the support surface such that the peripheral edge structure is rotatatable around a central axis located in the central region, 
 a mirror array including a plurality of elongated flat mirrors arranged in a low-profile, substantially horizontal plane and disposed in the central region, each elongated flat mirror being movably connected to and simply supported between corresponding portions of the peripheral edge structure such that said each elongated flat mirror is maintained in a corresponding tilt angle; and 
 a mirror positioning system fixedly disposed on the support surface adjacent to the carousel, the mirror positioning system including:
 a solar elevation tracking controller including means for adjusting the tilt angle of each of the plurality of elongated flat mirrors in accordance with a determined sun elevation angle such that sunlight directed onto the mirror array from said determined sun elevation angle is reflected by all of the plurality of elongated flat mirrors onto the solar receiver, and 
 a solar azimuth tracking controller including means operably connected to the peripheral wall for adjusting the rotational position of the carousel around the central axis in accordance with a determined sun azimuth angle such that sunlight directed onto the mirror array from said determined sun azimuth angle is reflected by all of the plurality of elongated flat mirrors onto the solar receiver.